In a low-deck vehicle such as a scooter-type motor cycle or motor tricycle, a technology in which an engine shaped like a letter V in the fore-and-aft direction is mounted at the lower portion of a vehicle body frame, and an air intake structure and an air cleaner structure are disposed above the engine is disclosed in JP-A-2001-88763. FIG. 28 is a schematic drawing of a low-deck vehicle which corresponds to FIG. 2 in JP-A-2001-88763. Parts shown therein are renumbered.
The low-deck vehicle 300 is a scooter-type motorcycle in which a power unit 320 is mounted in a double-cradle type vehicle body frame 310 at the position downwardly of a low-deck 318.
The vehicle body frame 310 includes a pair of left and right upper frames 312, 312 (only the left one is shown, hereinafter) extending from a head pipe 311 downward and rearward, a pair of left and right down frames 313, 313 extending downward from the head pipe 311, a pair of left and right center frames 314, 314 extending from the midsections of the down frames 313, 313 rearward and upward, a pair of left and right lower frames 315, 315 extending from the lower ends of the down frames 313, 313 toward the rear, and a pair of left and right rear frames 316, 316 for connecting the rear ends of the lower frames 315, 315 and the rear ends of the center frames 314, 314.
The rear ends of the upper frames 312, 312 are connected to the midsections of the center frames 314, 314. The low-deck 318 can be supported by the vehicle body frame 310. The low-deck 318 is a floor on which legs of an occupant is placed.
The power unit 320 includes an engine 321 shaped like a letter V in the fore-and-aft direction mounted at the front, and a transmission unit 331 mounted at the rear. The V-shape engine 321 is a water-cooling engine having a front cylinder 322 and a rear cylinder 323 formed so as to form a bank angle θ10 (angle θ10 between the cylinders 322 and 323) in the order of 45° in side view. The front cylinder 322 extends substantially horizontally toward the front. The rear cylinder 323 extends toward the head pipe 311. Consequently, the bank angle θ10 becomes a narrow angle in the order of 45° in side view. As a matter of course, a bisector L11 of the bank angle θ10 passes between the head pipe 311 and a front wheel 351. Reference numeral 324 designates a crankshaft.
Exhaust pipes 326, 326 connected to the respective cylinders 322, 323 extend below the engine 321 toward the rear and reach a muffler 327.
The low-deck vehicle 300 includes an air cleaner 340 disposed in a space between the head pipe 311 and the rear cylinder 323, an engine-cooling radiator 352 disposed between the engine 321 and the front wheel 351, a seat 353 disposed on top at the rear, and a front fuel tank 354 and a rear storage box 355 disposed under the seat 353.
The transmission unit 331 is provided with a power transmission unit 333 that is capable of swinging in the vertical direction about a final output shaft 332 as the swinging support end. A rear wheel 334 may be mounted to the power transmission unit 333 and the power transmission unit 333 may be suspended from the vehicle body frame 310 via a rear cushion 335. The rear cushion 335 is vertically disposed under the seat 353 between the fuel tank 354 and the storage box 355. Reference numeral L12 is a straight line passing through the head pipe 311 and the final output shaft 332.
The air cleaner 340 includes a filter element 341 in the interior thereof, an air intake port 342 on top thereof, and a lid 343 disposed on top for closing the air intake port 342. The respective cylinders 322, 323 are connected to the air cleaner 340 via air intake connecting hoses 344, 345, respectively. The air intake connecting hose 344 connected to the front cylinder 322 passes between the cylinders 322, 323 to the air cleaner 340. On the other hand, the air intake connecting hose 345 connected to the rear cylinder 323 passes over the rear cylinder 323 to the air cleaner 340.
However, the air cleaner 340 in the related art is provided with the lid 343 on top thereof. In order to attach and detach the filter element 341 disposed in the interior of the air cleaner 340, it is necessary to open the lid 343 on top. Therefore, it is not easy to secure a large space that can be used effectively above the air cleaner 340.
Accordingly, it is an object of the present invention to provide a technology to secure a large space that can be used effectively above the air cleaner.
Also, in order to secure ease of straddling the vehicle body when the driver rides on the vehicle, the vehicle body frame 310 shown in FIG. 28 is constructed in such a manner that the upper frames 312, 312 are significantly lowered toward the rear, and the rear ends thereof are joined to the midsections of the center frames 314, 314. In other words, since the upper frames 312, 312 and the center frames 314, 314 are combined into a substantially V-shape, arrangement of the engine 321 at the lower position is limited, and thus it is difficult to use a space above the engine 321 effectively while maintaining rigidity of the vehicle body frame 310. In addition, there is room for improvement regarding the relation between the vehicle body frame 310 and the air intake structure.
Accordingly, it is a further object of the present invention to provide a technology in which air can be supplied smoothly from the respective air intake structures to the respective cylinders of the V-shape engine while improving rigidity of the vehicle body frame.